The invention relates to antimicrobial and bactericidal compositions, and packaging and processing films for foodstuffs containing such compositions and a method for inhibiting or preventing growth of microbes such as bacteria, molds, and yeasts on food surfaces.
"Food preservation", as that term is used herein, includes methods which guard against food poisoning as well as methods which delay or prevent food spoilage due to microbes. Food preservation keeps food safe for consumption and inhibits or prevents nutrient deterioration or organoleptic changes causing food to become less palatable.
"Food spoilage", as that term is used herein, includes any alteration in the condition of food which makes it less palatable including changes in taste, smell, texture or appearance. Spoiled food may or may not be toxic.
"Food poisoning", as that term is used herein, refers to mammalian disease caused by ingestion of food contaminated by pathogenic viruses, molds or bacteria and/or their toxins. Pathogen-contaminated food does not necessarily show any organoleptic sign of spoilage. Bacterial food poisoning may be caused by either infection of the host by the bacterial organism or by action of a toxin produced by the bacteria either in the food or in the host.
Prevention of food spoilage and food poisoning has been attempted throughout history often through trial and error. The early attempts have resulted in the adoption of such food preservation methods as the drying, salting and/or smoking of foods in order to preserve them. It has been relatively recent in recorded history that food preservation has been placed upon a scientific foundation. In the nineteenth century, work of such scientists as Louis Pasteur and Robert Koch elucidated the bacterial causes of food poisoning and spoilage and provided new methods of identifying pathogenic bacteria and of preserving food.
Present food technologists utilize an array of physical, chemical, and biological processes and agents to preserve food and prevent the transmission of disease via foodstuffs. In addition to such processes as irradiation, fermentation, pasturization, control of temperature, pH and/or water activity, a plethora of chemical agents exist. These agents include antioxidants to prevent chemical degradation of food, as well as compositions which kill or inhibit deleterious bacteria and/or other microbes thereby preserving food i.e. preventing both spoilage and the transmission of disease. Commonly employed antimicrobial chemical agents include nitrites, nitrates, sulphur dioxide, sulfites, and acids such as acetic, propionic, lactic, benzoic, and sorbic acid and their salts, wood smoke and liquid smoke, and antibiotics such as natamycin and nisin.
Prevention of food poisoning is of paramount importance in the food processing industry. Concern for food safety has led most countries to heavily regulate the food industry to ensure public health. Also, manufacturers of processed food invest considerable resources to ensure the safety of their products. Despite these efforts, food poisoning still occurs. Many instances of food poisoning are attributed to bacteria such as Salmonella, Clostridium, and Staphylococcus among others.
Of rising concern is the relatively recent discovery in the food processing industry of widespread Listeria contamination of poultry and processed foods such as wieners, other sausages, cheese, dairy products including novelty ice cream, and seafood. Of particular concern is the recent evidence that pasteurized and fully cooked processed foods are being contaminated with microbes such as Listeria monocytogenes following cooking or pasteurization and prior to packaging for point of sale. Such contamination is typically surface contamination believed to be caused by contact of microbes with food surfaces subsequent to heat treatment (i.e. cooking or pasteurization). Microbes such as Listeria may be airborne (i.e. carried by dust) or present on food contact surfaces such as processing equipment.
In the 1980's several outbreaks of food poisoning have been reported worldwide in which the causative agent is suspected to be or has been identified as Listeria contaminated food. Outbreaks of listeriosis (infection by Listeria bacteria) in humans have been reported in Massachusetts, California, and Pennsylvania in the U.S.A. and also in Canada, and Switzerland. These outbreaks have been attributed to ingestion of Listeria contaminated food such as coleslaw, cheese made from raw milk, surface ripened soft cheeses, and salami. Hundreds of people have been affected with a mortality rate of up to about one third of those affected. Particularly susceptible to the disease (which is contagious) are pregnant women, fetuses, newborn and infant children as well as adults with compromised immune systems e.g. adults under treatment with immunosuppressive drugs such as corticosteroids. Listeriosis is a serious disease which may cause meningitis, spontaneous abortion, and perinatal septicemia. Although treatable with early diagnosis, untreated listeriosis exhibits a high mortality rate.
Food preservation by inhibition of growth of Listeria monocytogenes is difficult. Listeria can reportedly reproduce and grow both aerobically and anaerobically, at pHs above 4.85 and over a wide range of temperatures which can be as low as 3.degree. C. and as high as about 45.degree. C. This means that Listeria can grow at normal refrigeration temperatures. Listeria has also been reported as being able to grow in a water solution of up to 10% salt. Fortunately, cooking or pasteurization kills Listeria. Unfortunately, microorganism contamination may occur following pasteurization by the processor. Many people eat processed foods after a significant period of time has elapsed from a first cooking or pasteurization by the food manufacturer thereby permitting bacteria introduced by post-pasteurization contamination to grow. Since this food consumption may occur without reheating the processed food to sufficient temperatures for sufficient time to kill any microbes (such as Listeria) which may have been introduced subsequent to initial cooking, there is a risk of food poisoning. The present invention seeks to ameliorate the aforementioned risk.